After having run the network scan, my timeline is now flooded with messages reporting "Offline at" and "Last scanned at" attributes had been updated for each device on the network. The "Offline at" attribute in particular seems to get updated every hour or so as well. And these attributes do not appear to be in the configuration list, so I can't untick them, so that they are not reported.

Also while I could find "Last scanned at" info on each device page, the "Offline at" info doesn't seem to be shown anywhere but in the timeline.